My wife was a flight attendant and had to get a crash pad (rent an apartment) for work. Is that deductible?

Unfortunately, flight attendants cannot deduct the expense of a crash pad.  

1. Commuting expenses are not deductible.  The cost of getting to and staying at your tax home is considered to be a commuting expense.
2. Under the Tax Cuts and Jobs Act (TCJA) that Congress signed into law on December 22, 2017, the unreimbursed employee expenses deduction has been suspended in tax years 2018 through 2025.